I/O error during restore from sparse image

[delangea]

Hi! I'm trying to restore a smart-updated sparse image to an erase (and disk-utility checked and repaired) partition.
Both the OSs (the backup disk where the sparse image resides and the clean partition) are on Lion, installed on an other disk/partition.
I've tried it 3 times, every time, about 3 hrs in, I get a fail: Cannot restore, I/O error. Since this is under Disk Utility, I do not know how to access the log ti find what the actual problem is (and SD is not running).
What do I need to do?

[dnanian]

Why did you have to restore in the first place? Were you having drive problems on the internal? (I ask because reformatting and 'checking' with Disk Utility doesn't really affect low-level disk issues, and it doesn't really 'test' the drive.)

[delangea]

Hi Dave,
I need a restore to a second machine to have a 'standby' solution. I have now found that the source drive can not be fixed by DU. I have copied the sparse images elsewhere, am reformatting the source drive, will copy back and try again. It is surprising, though, that SD finds fault with a drive when it needs to restore from it, not with the same drive when it is smart updating a sparse image to it. But that remark may well be based on my ignorance as to the deeper process?

[dnanian]

It may be that the drive failed after the copy, or something happened to the image...

[delangea]

Or that the drive was still being shared by another computer?
I've switched off everything I do not need for the process, after I gfound that I could not eject the source drive (to run Disk Warrior), due to still being shared.
I've run DU again and now it does not register any problems. I will try the restore again.

[dnanian]

Make sure you repair the image, not just the 'host' drive.

[delangea]

Dave: Maybe size does matter after all. I was trying to restore a 110GB sparse image to a drive with 116GB space. I then created a new backup, which came in at 90GB. This backup finally allowed me to restore to my 2nd machine without a problem. Two questions: 1) how much extra space (over and above the size of the image) does SD need to restore and 2) over time and after many daily sequential backups, a sparse image grows well beyond the size of the drive being backed up. In my case, the drive (used) size is around 90 GB, the sparse image has now grown to 110 GB. What causes this and is it possible to 'shrink' the image closer to the source size, without making an entirely new backup?

[dnanian]

If the drive is empty, we don't need any additional space when copying from volume to volume. A sparse image, growing, is simply growing because of the way OS X manages free space on the virtual disk in the image.